In general, the world that contraception has made has been a world characterized by steadily declining marriage rates, steadily rising numbers of children born out of wedlock, birthrates that have fallen well below replacement levels across the developed West (threatening a very different kind of population crisis from the one you invoke), and millions upon millions upon millions of abortions.

Hmmm. Douthat's critical critique of contraception goes a lot further than Santorum's vague assertions, but his criticism could be made a tad more explicit. So let's probe this critique a little deeper and see where it leads us:

First, he says that "the world that contraception has made has been a world characterized by steadily declining marriage rates." It sounds to me like he is saying, "Contraceptive use destroys the institution of marriage, whereas unintended pregnancies preserve them." If that's accurate, he must also believe that banning or limiting contraceptive use would lead to a lower divorce rate. Or, in other words, more unintended pregnancies are needed to foster and preserve the institution of marriage. Hardly.

Second, he says that the world of contraception has been accompanied by "steadily rising numbers of children born out of wedlock." This time he appears to be saying that contraceptive use is responsible for children being born out of wedlock. And that reasoning, taken to its logical conclusion, would suggest that lowering contraceptive use would lead to fewer children being born out of wedlock. Really?

Third, he says that contraceptives have led to birth rates in the "developed West" that are "well below replacement levels." That would seem to suggest that the United States, whose total fertility rate (2.06) is just a hair below the commonly accepted replacement rate of 2.1, is not part of the "developed West." It would also seem to suggest that the drops in desired family size had little or nothing to do with the observed drops in fertility. Is he seriously suggesting that we should reduce contraceptive use (i.e. increase the number of unintended pregnancies) so as to avoid any further declines in fertility rates?

Fourth, he suggests that birth control usage is precipitating a "different kind of population crisis." That would seem to suggest that the world would be better off if we reduced contraceptive use and boosted birth rates. Higher birth rates in the developed world, including the United States, might stave off concerns about "aging" societies, but does he really believe that faster population growth would be beneficial in terms of climate change, water scarcity, pollution, food security, the energy crisis, environmental degradation, or the extinction of plant and animal species?

Fifth, he argues that the world of contraception is responsible for an increase in abortion rates. Does he really believe that reducing contraceptive use and increasing the number of unintended pregnancies in the world will somehow reduce the number of abortions? What kind of perverse thinking is that?

There's a basic misconception that clouds Douthat's thinking about contraception, and it's one that is shared by many other social and religious conservatives. Believing that contraceptive use is a moral wrong, they desperately want to make it into a social ill. And to do that, they confuse correlation with causation. In other words, bad things have happened since the widespread introduction of the birth control bill and, ergo, it must be the root cause of those bad things.

A lot of factors may have led to greater promiscuity, higher divorce rates, and more single-parent households. In the past half-century, entertainment media have helped turn us into a sex-obsessed culture, divorce laws have been significantly relaxed, and -- most significantly, perhaps -- higher living standards have made it easier for couples to divorce and for single-parents to raise children. But if you believe that contraception is morally wrong, it's a lot more convenient to rail against the "dangers of contraception" than to take on entertainment media, argue for stricter divorce laws, or advocate for lower standards of living.

Believing that the use of contraception breaks a religious rule or tenet is one thing. Arguing that it is a social ill is quite another. Ross Douthat and other critics of contraception should understand the difference.